As a conventional vehicle seat, there has been proposed a vehicle seat which includes a seat cushion, a seat track mechanism for allowing the vehicle seat to be moved forward and rearward in a vehicle, and a mechanism for causing the seat cushion to rise and fall in order to adjust a height of the vehicle seat. Japanese Patent Application Laid-Open No. 2002-142908 discloses the conventional vehicle seat. The seat cushion of the vehicle seat comprises a frame structure, a plurality of zigzag springs stretched in the frame structure, and a cushion member supported to the frame structure so as to be laid on the zigzag springs, and combined with the frame structure.
The frame structure is formed into a substantially quadrilateral ring-shape and comprises a pair of spaced apart side frame members, a first connecting shaft arranged between rear end portions of the spaced apart side frame members, and a front frame member fixed to forward end portions of the spaced apart side frame members. The zigzag springs are coupled at both terminals thereof to the front frame member and the first connecting shaft.
The seat track mechanism comprises a pair of parallel stationary rails spaced apart from each other and mounted on a floor of the vehicle through brackets, and a pair of parallel movable rails spaced apart from each other and slidably engaged with the stationary rails.
The mechanism for causing the seat cushion to rise and fall comprises linkage means provided between the movable rails and the side frame members of the frame structure. The linkage means comprises a pair of forward and rearward linkage bars connected at both ends thereof to each of the movable rails and each of the side frame members. More particularly, the forward linkage bar is pivotally supported at one end thereof through a first support pin to a portion of a corresponding movable rail which is adjacent a forward end portion of the corresponding movable rail, and supported at the other end thereof through a second support pin to a portion of a corresponding side frame member which is adjacent the front frame member. A second connecting shaft is arranged between forward linkage bars connected through second support pins to the side frame members, and coupled at both ends thereof to the second support pins. The rearward linkage bar is pivotally supported at one end thereof through a third support pin to a portion of a corresponding movable rail which is adjacent a rearward end portion of the corresponding movable rail, and supported at the other end thereof through a fourth support pin to a rear end portion of a corresponding side frame member of the frame structure. The first connecting shaft is arranged between rearward linkage bars connected through fourth support pins to the side frame members, and coupled at both ends thereof to the fourth support pins and the rearward end portions of the side frame members.
The forward and rearward linkage bars are adapted to be actuated by a driving motor or an operating knob so as to be pivoted. When the forward and rearward linkage bars are pivoted in a predetermined direction by the driving motor or the operating knob so as to operatively stand up, the vehicle seat is lifted up. When the forward and rearward linkage bars are pivoted in the opposite direction so as to be operatively inclined, the vehicle seat falls.
In a case where each of the zigzag springs is coupled at a rear terminal thereof directly to the first connecting shaft, when the first connecting shaft is moved as the linkage members are pivoted and the seat cushion rises, the rear terminal of the zigzag spring is wound around the first connecting shaft, whereby the zigzag spring may be twisted and irrecoverably deformed. Furthermore, it take a lot of labor to couple the rear terminals of the zigzag springs directly to the first connecting shaft by welding for example. In order to overcome the problems, the rear terminals of the zigzag springs of the conventional vehicle seat are coupled to the first connecting shaft through retainers.
Referring now to FIGS. 1 and 2, the conventional vehicle seat will be discussed in greater detail hereinafter in order to facilitate understanding of the present invention. In the conventional vehicle seat, a round pipe is employed as the first connecting shaft J of the frame structure. The zigzag springs S (only one zigzag spring S is shown in FIGS. 1 and 2) are coupled at forward terminals thereof directly to the front frame member F of the frame structure, and coupled at rearward terminals thereof to the first connecting shaft J by substantially S-shaped retainers R (only one retainer R is shown in FIGS. 1 and 2). Each of the retainers R comprises a first substantially C-shaped section r1 and a second substantially C-shaped section r2 continuing from the first C-shaped section r1. First substantially C-shaped sections r1 of the retainers R are rotatably mounted on the first connecting shaft J. The rearward terminals of the zigzag springs S are hooked on second substantially C-shaped sections r2 of the retainers R.
The rearward terminal of each of the zigzag springs S is merely hooked on a corresponding retainer R and supported to the retainer R at one point thereof, so that when a person P sits on the vehicle seat and a weight load of the person P is then applied to the seat cushion, the retainers R are rotated around the first connecting shaft J in a clockwise direction while being pulled downwardly at the second substantially C-shaped sections r2 thereof as shown in FIG. 2. Therefore, when compared with zigzag springs coupled at rearward terminals thereof directly to the first connecting shaft, the zigzag springs coupled at the rearward terminals thereof to the first connecting shaft through the retainers are considerably flexed downwardly as the retainers R are rotate in the clockwise direction while being pulled downwardly. The downward flexing of the zigzag springs deteriorates a cushioning condition of the seat cushion.
Furthermore, the retainers R are each formed into a substantially S-shape, so that each time the weight load of the person is applied to the seat cushion, the retainers R are drawn downwardly by the weight load and gradually deformed. As a result, when the person sits on the vehicle seat several times, the retainers R are irrecoverably deformed.